Strip enclosures, doors and windows recently have become popular wherever there are high levels of traffic between two areas whose environmental conditions must be separated. For example, in walk-in freezer applications, strip doors enable sub-zero temperatures to be sustained inside the freezer without undesirable loss of the cold air, thereby saving energy and money. Strip closures also can be used to provide walkthrough doors, or passthrough windows when it is desired to keep a particular installation warmer than the outside ambient temperature. In some applications they are ideal for preventing movement of heavy industrial dust, dirt and contaminates from one area in a facility to another to reduce cleanup costs and improve the general appearance of the facility. Since the strips can be constructed from relatively economical material, their initial installation cost is relatively low. The strips also can be constructed from transparent material to eliminate the safety hazards inherent in blind opening doors and can be effective to reduce sound transmission by significantly cutting down noise transmitted from a source surrounded thereby without impairing access to the noise source. They can be used to control airborne particles by preventing the spread of dust, smoke and sparks by enclosing them in the areas where they originate and to prevent the entry of birds and flying insects.
Heretofore, strip closures have been installed by clamping the upper portion of each strip to a hangar assembly or by looping the strips over a rod installed adjacent the top of the opening to be covered. Both methods have disadvantages. Since the strips must overlap to form a barrier effectively, either the looping or the clamping installation system requires the removal of strip material adjacent the support which weakens each of the strips in the area where its strength needs to be greatest. In the looping system, all of the strips must be installed on the hanger rod before it is installed so that the installation, especially over a large opening, requires more than one person and once installed the entire assembly of strips must be removed to replace single strips or to successfully clean the ones in place. With the clamping system, bolts usually are provided to squeeze two structural members about the tops of the strips. The bolts pass through holes in some of the strips which tend to rip during use, and not being flexible, the structural members cause the strips to bend adjacent the bottom thereof causing stress concentrations which eventually cause the strips to break off.